British Patent Application No. 2,184,321A discloses a confocal scanning microscope having a scanning system that imparts a two-dimensional transverse scan to a laser beam. The scanning system utilizes a rotating polygon mirror to effect line scanning and a galvanometer-driven mirror to effect frame scanning. The scanned beam is passed through a microscope eyepiece and objective and is focused on a sample. Fluorescent light emitted by the sample is returned along most of the same beam path (thereby being de-scanned) and is directed to a detector by a suitable beam splitter. Optical telescopes are used for optical coupling along the optical path of the incident and return beams.
The prior art system works well, but the optical quality of the telescopes must be high. Moreover, the system is not achromatic and does not necessarily perform well at all wavelengths.